Field of the Invention
The present invention relates to the field of position detection and, specifically, to a device for transmitting movement to a position sensor and to a position-detection device including such a transmission device.
Brief Discussion of the Related Art
In the field of aeronautics, it is known to detect the position of flight-control instruments, such as a control stick, by means of position sensors comprising an input formed by a toothed element. A movement-transmission device is mounted between the toothed element and the control instrument such that a predetermined movement of the flight-control instrument causes a corresponding movement of the toothed element. In the case of a pivotably mounted control instrument, the transmission device includes, for example, an input shaft rotatably linked to the instrument and to an output shaft supporting a toothed sector meshing with a toothed pinion forming the input of the position sensor.
Due to high-precision control requirements, the presence of play in the transmission of movement between the toothed sector and the toothed element is not acceptable. Said problem has been solved by splitting the toothed sector into a first toothed sector rotatably linked to the output shaft and a second toothed sector mounted coaxially to the first toothed sector in order to have an angular displacement relative to the first toothed sector. Return springs are mounted between the toothed sectors in order to return the second toothed sector into a predetermined position such that the tooth of the engaged toothed element is clamped between two teeth each belonging to one of the toothed sectors. The return springs are sized such that the tangential force to be transmitted to the toothed element is smaller than the return force. Thus, there is no play between the toothed sectors and the toothed element.
However, the risk exists that one of the springs may break, that pieces may come loose and affect the operation of surrounding devices, such as other position sensors. The springs are attached to the toothed sectors by means of hook portions: in order to prevent the hooks from breaking and pieces from coming loose, it has been foreseen to cover said portions with a resin. In order to prevent the turns from coming loose, it is known to insert a core in the springs. Said solutions make it possible effectively to remove the aforementioned risk, but the implementation thereof requires manual operations that make it more expensive to manufacture the transmission device.
The second toothed sector is usually retained on the first toothed sector by an axial abutment attached to the first toothed sector by screws. It is important that said screws do not come loose in order to ensure the firmness of the axial abutment and to prevent one of said screws from coming out and affecting the operation of the surrounding devices. Since said screws have a small diameter, the only known means for preventing the loosening of screws is to glue them. When performed manually, said operation also increases the cost of manufacturing the device.